Search

A recombinant strain of vaccinia virus (VR26) containing a DNA-copy of the subgenomic 26S RNA of Venezuelan equine encephalomyelitis virus (VEE) inserted into the coding region of thymidine kinase (TK) gene was produced. This subgenomic RNA contained the genes for all structural proteins of the VEE virus, the strain Trinidad donkey (TRD). VR26 effectively expressed VEE virus glycoproteins on the membranes of the infected cells. Blood sera of VR26-immunized animals were found to contain VEE virus-specific antibodies. VR26-immunized mice and rabbits showed a high level of resistance to subcutaneous inoculation with the pathogenic TRD strain of VEE virus. VR26 also provided a high level of protection in animals against aerogenic infection. The absence of virus-neutralizing antibodies in most VR26-immunized animals resistant to inoculation with high doses of VEE suggests the dominant role of the cell component in the immune response. The immune response induced by the recombinant VR26 strain was stable as demonstrated by the resistance of the animals to a challenge with VEE virus 7 months after immunization. The experimental results suggest that this recombinant strain may be considered as a candidate for vaccine preparation.

Genomes of vaccinia strain L-IVP and its cloned variants were investigated by restriction and Southern blotting analysis. The strain L-IVP was shown to be heterogeneous and to consist of variants which differed in the genome structure and properties. Clone 1 derived from L-IVP was less reactogenic than the original strain for rabbits inoculated intradermally and had mutations in the right terminus of the genome. All the clones were stable in passages in the chorioallantoic membranes of developing chick embryos and roller BHK-21 cell cultures.